Temperature-indicating system.



G. w. LEVENGOOD.

TEMPERATURE INDIGATING SYSTEM.

APPLICATION FILED AUG. 27, 1909.

966,224. Patented Aug. 2, 1910.

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ATTORNE Y8 GEORGE W. LEVENGOOD, OF LEBANON, PENNSYLVANIA.

I TEMPERATURE-INDICATIN G SYSTEM.

$pecification of Letters Patent.

Patented Au a, rain.

Application filed August 27, 1909. Serial No. 514,937.

invented certain new and useful Improvements in Temperature-Indicating Systems, of'which the following is a specification.

My invention relates to improvements in devices for indicating at a central station abnormal temperatures of rooms, dwellings or inclosures situated some distance fromthe central station and it consists in the combinations, constructions herein described and claimed.

An object of my invention is to provide a device whichmay be located at the place at which the temperature is to be kept within certain limits so that on the undue variation of the temperature, as in case of fire, indication of such variation will be given at the central station.

A further object of my invention is to provide means by which the operator at the central station can determine. whether or not the indication is caused by an accidental disarrangement of the circuit or whether it is really due to a decided change in temperature.

A further object of my invention is to provide a thermostat for use in my system which may be regulated by varying the current strength at the central station, and

' which will operate when the temperature reaches a redetermined point.

Other 0 jects and advantages will appear in the folldwing specification and the novel features of the device willbe particularly pointed out in the appended claims.

y invention is illustrated in the accom panying drawings in which F igure 1 is a perspective view of the adjusta 1e thermostat which forms the main feature of my system; Fig. 2 is a longitudi' nal section through the compound bar of the thermostat; Fig. 3 is a vertical section along the line 3-3 of Fig. 2; Fig. 4 is a vertical section along the line 4-4 of Fig. 2, and F ig.'5 is a diagrammatic view of the circuits of the svstem.

Incarrying out my invention, I provide aninSulating base 1 having the slots 1, 1 and 1 upon which is mounted a pair of magnets 2, these magnets being preferably wound with a large number of turns of fine wire. Secured to the base on a line midway and arrangements between the magnets is an adjustable standard 3 which is adjustable toward and away from the magnets 2, in the slot 1". The standard 3 is screw-threaded to receive a milled nut 4 and a winged nut 5 between which the end of a compound bar (3 is secured. The structure ofthis compound bar is clearly shown in Figs. 2 and 5. It consists of an upper metal strip (3 having a coefficient of expansion which is relatively low, and a lower bar 6* of a different shape and having a relatively high coefficient of expansion. The free end of the compound bar is provided with an armature 6 having screw-threaded openings 6 in its ends, these openings being located immediately above the centers of the respective magnet cores. Disposed in these openings are the screws 6 each provided with a lock nut 6. The armature 6 is provided with a platinum contact 6 Between the magnets 2 and the standard 3 are a pair of standards 7 and 7, the former being adjustably mounted in the slot 1 and the latter in the slot 1. These standards are also screw-threaded for the reception of the lower milled nuts 8 and 8 and the upper win ed nuts 9 and 9', res ectively- Supported between the standar s 7 and 7 is the transverse conducting member 10 which bears a laterally projecting arm 11 beneath which is secured the spring 12, the free end of the spring being bent upwardly above the end of thearm 11 and being provided with a platinum contact 13 arranged to engage the platinum contact 6 on the member 6. The. arm 11 is for the purpose of bracing the spring and limiting its upward movement. A condenser 1% may be arranged for convenience on the plate 1.

In Fig. 5 I have shown a Working circuit which may be used in my system although other specific arrangements of parts might be made without departing from the spirit of the invention.

In Fig. 5, AC denotes an alternating current generator; DC is a source of direct current such as a battery. One terminal of the battery is connected by the conductor 15 with the contact 16 which is normally in engagement with a spring conductor 17. The latter may be pushed downwardly out of engagement with the contact 16 into engagement with the contact 18 by means of a button 19. The contact 18, it will be ob served is connected to one side of the alterrheostat is a wire 25 which leads to the magnet 26 of arelay. The armature 27 of the relay forms part of a local circuit in which the battery 28, the alarm bell 29 and a switch 30 form the remaining parts. The

armature 27 is normally held against a contact 31 by means of a spring 32. One terminal' ofthe relay is-in turn connected. with a variable resistance 33. The thermostatic elements are connected with the spring 17 in the manner shown in the figure. I have illustrated two of 'such instruments as being connected in series in one circuit although it will be understood that more than two might be used in one circuit, the connections of the other instruments being similar to that shown. In the diagram it will be-seen that the compound bar 6 is connected by the conductor 34 with the spring 17, a condenser 14 being inserted between the bar 6 and the spring 12, the latter being connected to the magnet 2 b the conductor 35. The second instrument as similar parts,'the compound bar being'connected with the terminal of the magnet 2 of the first instrument in the manner shown.

From the foregoing description of the various parts of the device the operation thereof may be readily understood.

Each of the thermostatic elements is calibrated before leaving the factory, at a certain tem erature say degrees. -The contact 6 0 the compound bar will stand at a certain distance above the contact 13 of the spring. Now if a higher temperature should occur the buckling of the bar upwardly due to the unequal expansion of the two metals will cause the armature to lift farther away from the spring and also farther away from the magnet cores. It is obvious that it will take a greater current to again attract the armature than it would at a lower temperature when the armature is nearer the magnet poles. On the other hand, if the term perature should decrease, the armature will approach the magnet poles and a less cur rent will be required for the armature to efiect the engagement of the contacts. This principle forms one of the main features of the invention. The use of the variable resistance 33 will be explained later.

With the s stem arran ed as shown in Fig. 5, we w' first'eonsi er the operation' necessary to set the thermostatic device so that it will sound an alarm at a-given temperature, say or above. The operator at the central station places the indicating pointer of the rheostat 22 at 140, thereby cutting out all of the resistance of the rheostat. (Obviously the scale might be arranged with indications higher than 140,

this being purely an arbitrary matter.) He now presses the button 19. connecting the alternating current generator with the two thermostatic elements, thereby sending a current over the following path from the generator, through 20, 18, 17, 34, condenser L1, 35, "gmagnet- 2, 3 1', condenser 14', 35, magnet 2, 36, 33,26, 25, 22, 21 and back to the generator. The connection with the battery is broken, of course, at 16 during the movement of the key 17. The pulling down of the armatures 6 and 6 of the thermostats causes the engagement of the contacts 6 and 6 with t e springs 12 and 12', respectively. The button 19 is now released, thealternating circuit is broken, and the direct current circuit established at 16. The tendency of the armatures 6 and 6 is to fly back again, but they are followed in their upward movement by the springs 12 and 12' so that before the contacts 6 13, 6 and'13'- are broken, a direct current is established through these contacts and through the magnet aroundto the battery. This keeps the magnets closed. The operator now moves the pointer of the rheostat 22 down, thereby switching in resistance and decreasing the current through the magnets, which will eventually let go when the current becomes so weak that 1t cannot retain the spring armatures. which the instrument is situated "is at 70 when the pointer indicates 70 on the rheostat 22. If the room is at a higher temperature, it will occur before the pointer reaches 7 0 and will indicate the temperature at which the room is. The retraction of the This will occur if the room in armatures of the thermostatic devices breaks pressed at the same time that the key 23 is 1n contact with its spring This will cause both magnets 2 and 2 to again be energized. Keys 19 and 23 are now released and the thermostat will operate whenever the temperature of the room in which it is located reaches 75. Of course, the rheostat dial might have been set at 80 instead of 75,

something to be wrong,

or at any other temperature at which it is desired to operate the device.

The testing and resetting of the device is supposed to be conducted at predetermined intervals so that the operator can keep direct account of the temperatures of the rooms or fiaces at which the devices are stationed.

e accomplishes this by moving the rheostat pointer back toward 0. As soon as the temperature of the room is reached (the temperature might have risen, say to 73), the thermostat will let go, thereby sounding the alarm, and indicating the temperature at which the room is now. The resetting of the instrument maybe accomplished in the same manner as before and the instrument is preferably set 5 higher than the temperature of the room, this time being set at The rise of tem rature in the room above 78, therefore,'w1ll cause the device to operate. If the device should operate, the attendant termine whether it is a false alarm or whether the temperature is actually rising by proceeding as follows: He first presses the ey 23, thereby shunting the rheostat 22. The key 19 is then pressed, which causesthe magnets 2 and 2' to pull down the armatures. He then releases the keys 19 and 23 in consecutive order. If a. false alarm had been 'ven, the armatures will not let go, but if t ere is an abnormal rise of temperature, then the armatures will let go, even if the rheostat hand is pushed around several degrees higher than the operative point, therey provmg conclusively that there is a dangerous rise in temperature.

It will be noted that the thermostatic instruments are connected up in series. Since there must be a current of given strength when the rheostat indicates a given temperature, an additional resistance 33 is necessary when adding another instrument to the line. The resistance 33 is placed in circuit for a given, amount of resistance added for each additlonal thermostat in circuit, the same amount of resistance may be out out of the circuit by the variable resistance 33, thereby leaving a uniform resistance on the line and pernnttin more or less of the instruments to be added as occasion demands.

While I have shown one circuit entering the central station, it will be noted that in actual practice there are more circuits, and the attendant is supposed to test each one of these circuits at predetermined intervals. The alternating current frequency may be so high as to cause the magnets .2 and 2' to operate, or a lower frequency may be used, which will cause them to buzz or hum, thereby attracting attention in the dwellings themselves, so that if the operator believes he may thus sound the alarm for the occupants of the dwelling. The action of the thermostatic elements may at the central station may de-' so that be properly adjusted by means of the screws 6 These screws, as stated before, bear on the upper parts of the pole pieces. -It is obvious that the screws may be turned so that their lower ends will contact with the pole pieces when the armature 6 is at different distances from the' pole pieces. Thus, if they are screwed down, the armature may be lifted a considerable distance from the pole pieces, and hence, will more easily spring away from the pole pieces as the current is decreased. The instrument can thus be rendered'more or less sensitive.

I claim:

l. A temperature indicating system, comprising a central station, a source of direct current, and a source of alternating current at said central station, a thermostatic device provided with a magnet, means for connectmg the magnet with the source of alternating current, said means alsooperating-to cut off the alternating current and toconnect the direct current for causin the operation of the thermostat at any pre etermined temperature, a relay in circult with said thermostat, and a local circuit controlled by the relay, eating the operation of the thermostat.

2. A temperature indicating system com prising a central station, a source of direct current and a source of alternating current at said central station, a thermostatic device, connections between said thermostatic device and said sources of current, a key for connecting either the alternating or direct current source with said thermostat, andfor cutting out the other source, an indicating rheostat in said circuit connections, a relay controlled by said thermostatic device, and a signaling circuit controlled by said relay.

3'. A temperature indicating system comprising a central station, a source of direct current, and a source of alternating current at said station, an indicating rheostat, a relay, a local circuit controlled by said relay and provided with a signal, a thermostatic device comprising a magnet and a condenser in series wlth sald relay and said rheostat, and an armature and a contact spring in shunt circuit around said condenser, said shunt circuit being broken normally, said condenser being normally connected with said sources of direct current and a key for cutting oil the direct current and for switch,- ing on the alternating current, thereby operatlng the magnet of the thermostat, said key being arranged to close the direct current circuit beforethe actuation of the armature controlling the shunt circuit.

4. A temperature indicating system comprising a central station, a source of alternating current and a source of direct current at said central station, an indicating rheostat, a relay, a local circuit controlled by said relay and provided with a signal, a variable and provided with a signal for indi- &

resistance, a plurality of thermostatic devices each comprising a magnet, an armature, a contact spring arranged to be engaged by said armature, and a condenser having a shunt circuit, the said rheostat, relay, variable resistance, magnets, and condensers being in series, the actuation of the armatures of said magnets serving to control the shunt circuits around their'respective condensers, normally closed connections between one of said condensers and said source of direct current, and a key for switching on the source of alternating current whereby the magnets are energized, said key being arranged to cut off said alternating current and to switch on said direct current again, whereby the energization of the magnets is continued through the respective shunt cir- 'cuits around their respective condensers.

5. The combination with a central station provided with an indicating rheostat, of a thermostatic element comprising a magnet and a condenser in series with said rheostat, a spring armature having at one end a compound bar, a spring contact adapted to be engaged by said armature, said armature and spring contact being arranged to form a shunt around said condenser and means for adjusting the sensitiveness of the thermostatic device. x

6. In a temperature indicating system, a thermostatic device comprising a magnet, an

' armature therefor, comprising a compound bar and a spring support therefor, a contact spring, contacts on said armature and said eeaaea contact spring, a condenser between .said armature andsaid contact spring and means for regulating the movement 0d the armature toward said magnet, thereby varying the sensitiveness of the instrument.

7. In a temperature indicating system, a thermostatic device comprising'a magnet, an armature therefor, consisting of a compoundbar, a spring contact arranged to be engaged by the armature in its movement toward the magnet and adjustingscrews carried by the armature and adapted to engage the'magnet for adjusting the range of movement of thearmature toward the magnet.

8. A temperature indicating system com 54) station, a source of direct current, and a source of alternating current at said central station, a thermostatic device provided with electromagnetic operating means, means for connecting the 'electro 55 magnetic operative means with the source of alternating current, said means also operating to cut 03 the alternating current and to connect the direct current for causing the operating of the thermostat at any predetermined temperature, a relay in circuit with said thermostat, and a local circuit controlled by the relay-and provided with a signal for indicating the operation of the thermostat.

GEORGE W. LEVENGOOD. Vitnesses:

J08. REINHARD, S. J. PICKERING.

prising a central 

